NEW YORK, May 23 (Reuters) - Wegelin & Co, the oldest Swiss private bank, is digging in its heels against a U.S. criminal charge that it conspired to help wealthy Americans evade taxes.

At a hearing in U.S. District Court in Manhattan on Wednesday, a federal prosecutor said Swiss police on May 2 had hand delivered a court summons and a copy of the indictment to Wegelin executive Konrad Hummler.

The bank is now seeking to contest the summons in Swiss courts, prosecutor Daniel Levy said.

The indictment of Wegelin, which was founded in 1741, was the first in which the United States accused a foreign bank, rather than individuals, of helping Americans commit tax fraud.

Wegelin was accused of helping clients hide more than $1.2 billion in offshore bank accounts. The case is part of a U.S. crackdown on alleged tax fraud, including efforts to pierce the tradition of Swiss bank secrecy.

Wegelin was not in court on Wednesday, nor did it appear at the first hearing in the case in February.

A spokeswoman for Wegelin could not immediately be reached for comment.

At Wednesday's hearing, Judge Jed Rakoff conceded that it is "rather hard to arrest a corporation" but asked why U.S. prosecutors had not sought a warrant to arrest individual Wegelin partners.

There is "some reason to believe the Swiss authorities would not execute the warrant," Levy responded, but said he would continue to consider that as a possible option. No Wegelin partner has been charged, Levy said.

The case is U.S. v. Wegelin & Co et al, U.S. District Court, Southern District of New York, No. 12-cr-00002. (Reporting By Basil Katz; Editing by Phil Berlowitz)